The present disclosure relates to a latch mechanism for latching a first panel to a second panel to prevent the first panel from opening with respect to the second panel, and in particular to a pressure relief latch mechanism used for securing dual purpose aircraft doors which can open at a predetermined internal pressure or opened from the exterior for routine maintenance and inspection purposes.
One application for such pressure relief latches is on aircraft engine cowls. Aircraft engines have high internal operating pressures, and aircraft designers wish to have the pressure release latch not operate until the internal pressure approaches very close to the maximum permitted pressure. Thus, the tolerances on adjustment and operation of the release latch become tighter and the requirements for repeatability become more intensive. The pressure relief latch is adjusted at the factory to operate at a specific pressure. Failures are sometimes encountered in the field after many hours of usage, and the aircraft operator desires assurance that the pressure release latch will operate when needed and will not operate prematurely. Variations in friction and contamination from use can affect the operation of the latches. Temperature changes can also affect latch operation by causing variations in spring rate, which may affect the latch effective release pressure.